Obama has said he will overturn Bush's restrictions on embryonic stem cell research.

(CNN) - A group of six moderate House Republicans have written to President Obama urging him to lift President Bush's ban on federal funding for embryonic stem cell research.

"We are writing to respectfully urge that you immediately lift the current federal restrictions on funding for embryonic stem cell research," they wrote Wednesday, also requesting that the president ask the National Institutes of Health to issue "appropriate guidelines."

The letter was signed by Reps. Fred Upton of Michigan, Charles Dent of Pennsylvania, Brian Bilbray of California, Michael Castle of Delaware, and Mark Steven Kirk and Judy Biggert of Illinois.

Bush announced in August 2001 that his administration would allow federal funding only for research on about 60 stem cell lines that existed at the time, but Obama stressed on the campaign trail that he planned to reverse Bush's regulations and emphasize science over ideology.

"I guarantee you that we will sign an executive order for stem cells," Obama told a retreat of House Democrats in Virginia earlier this month. But some supporters of stem cell research have griped that Obama has not acted quickly enough to overturn Bush's ban.

"While we have been encouraged by recent news reports that you plan to issue an Executive Order soon, we cannot stress enough the importance of swift action," the moderate GOP members of Congress wrote Wednesday. "After the current restrictions are lifted, we stand ready to work with you and our colleagues in Congress on adopting complimentary legislation."

The Republicans said that stem cell research holds "great promise" for Americans suffering from afflictions like Parkinson's disease, spinal cord injuries and diabetes.

Burris admitted this week he had several discussions about fundraising with Blagojevich.

WASHINGTON (CNN) - Illinois Sen. Dick Durbin said Wednesday that a Senate ethics panel is investigating Sen. Roland Burris following his disclosure that he had spoken with Rod Blagojevich's brother about raising money for the disgraced former governor while seeking appointment to the Senate.

Durbin’s comments came shortly before Rep. Phil Hare, a Democrat from western Illinois, became the first member of Congress to publicly call on Burris to step down, describing the ongoing Blagojevich saga as “a recurring nightmare.”

“Given this latest revelation, I believe it is in the best interest of all Illinoisans that Senator Burris resigns,” Hare said in a statement. “Our state and its citizens deserve the whole truth, not bits and pieces only when it is convenient.”

Durbin, a member of the Senate Democratic leadership, told reporters during a congressional trip to Europe that “the Ethics Committee of the Senate is undertaking an investigation.”

“That is the appropriate thing at this point,” Durbin said.

He added that public statements by Burris in recent days “have raised questions which need to be looked at very carefully, as to the nature of his relationship with the former governor and the circumstances surrounding his appointment.”

Burris defended himself in another press conference Wednesday, and said he welcomed any investigations into his actions by the Senate or the state of Illinois.

“I ask you today to stop the rush to judgment,” he said. “You know the real Roland. I’ve done nothing wrong and I have absolutely nothing to hide.”